Discharge printing and fabric produced thereby



Patented Apr. 25,1933

cAMILL nEEYrUs, or New YORK, N. Y., nn GEORGE SCHNEIDER, 0F 'mon'rcmm,

s PATENToFFIc NEW JERSEY, LASSIGNORS CELANESE CORPORATION OF AMERICA, ACORPOBA TIQN OF'DELAWABE i DISCHARGE PRIM I NG AND FABRIC. PRODUCED.THEREBY No Drawing.

with dyestuffs that cannot be discharged by the ordinary methods nowemployed. I y

A further object. of our invention is to discharge-print fabrics bymeans of chro mate or dichromate in the presence of an acid. Furtherobjects of our invention will appear from the following detaileddescription.

The production of designs on colored backgrounds,-on fabrics containingorganic derivatives of cellulose, particularly :cellulose acetate, hasheretofore offered serious difiiculties, since many of the dyes thatcolor such fabrics cannot be discharged by the ordinary dischargemethods that employ reducing agents such as hydrosulphites,formaldehyde-sulphoxylates etc. We have found that many of suchdyestuffs may be discharged by the employment of a chromate ordichromate in the presence of an acid.

In accordance with our invention, we discharge print fabrics, andparticularly fabrics containing yarns of organic derivatives ofcellulose, which have been dyed with a suitable dye, whose color can bedischarged by a dichromate or chromate in the presence of an acid. Thepaste that we employ for discharge printing contains a chromate ordichromate, and in order to effect the discharge 1 of the color, asubstance containing an acid is applied to the fabric either before orafter the application of the printing paste containing the dichromate orchromate.

\Vhile any fabric may be treated in accordance with out invention, itisparticularly applicable to the treatment of fabric containing yarnsoforganic derivatives of cellulose, such as organic esters of celluloseand cellulose ethers. Examples of such organic esters of cellulose arecellulose acetate, cel- -App1icati6n filed May 6,1930. semi no. 450,309.

lulosejormate, cellulose propionateand cellulose butyrat'e,.whileexamples of cellulose ethers are ethyl cellulose, methyl cellulose andbenzyl'cellulose. The fabric may consist wholly of yarns containing oneor more organic deriva'tives'of cellulose, or it may be a mixed fabriccontaining yarns of organic derivatives of cellulose and yarns of otherfibres. Examples of such mixed fabrics are mixed cellulose acetate andreconstituted cellulose, mixed cellulose acetate and cotton andmixedcellulose acetate and wool. I

paste is previously dyed or colored with any suitable dye whose colormaybe discharged bythe oxidizing action of the chromate or dichromate inthe presence of an acid. When thefabric contains yarns of organicderiva: tives of cellulose, it is preferably dyed. with dyes that arenormally'insoluble in water, but which are dispersed or solubilized by adispersing agent such as a sulpho fatty acid,

Thefabric to be treated with the discharg particularly sulpho ricinoleicacid (Turkey red oil). We have found that water insolublecolorin'gbodies of the anthraquinone series, or alkyl or other nuclearor N-substitution products thereof are particularly amenable.

to this process. However the fabric maybe dyed with other dyestuffs thatare dischargeable by oxidation, and such dyestuffs may be of the di-ortriarylmethane, thiazine, oxazine, azine, azo, xanthene and indigoidseries.

The printing paste that is employed for obtaining the dlscharge Jprintscontains a dichromate or chromate,.whi'ch ispreferably water soluble,such'as the chromate of sodium or potassium and the dichromate of sodiumor potassium.

Inorder to effect good discharge, the presence of an acid is necessary.The acid may be employed in the formof a solution which is pre thedischarge paste. However excellent reerably applied after theapplication of sults are also obtained when the acid is aps plied to thefabric before the application of the discharge paste. Any suitable acidmay be used, examples of which are solutions of carboxylic acids such ascitric acid, tartaric acid, acetic acid, benzoic acid, or even diluteaqueous solutions of mineralacids such as hydrochloric acid and sulfuricacid. The acid may be applied to the fabric by padding or in any othersuitable manner.

Of the thickening agents that may be employed in making up the paste, itis preferable to employ such agents that are not appreciably affected bythe chromates or dichromates. The following are suitable: gumtragacanth, tragasol, British gum or other dextrines, water solublecellulose ethers, feculose (acetylated starch), agar agar, starches andmineral thickening agents or gelatinous masses, such as those producedby acidifying aqueous solutions of soluble silicates.

If color discharge prints are desired, there may be added to theprinting paste, dyestuffs or pigments that are resistantto oxidation.These may be of the pigment type, mineral pigment type, vat dyes of theanthraquinone series which resist the action of oxidizing agents, orother suitable dyestuffs. Examples of such dyestuffs are Methylene blue(Color Index No. 922), Rhodamine 6G Extra (Color Index No. 752), ormineral pigments such as Chrome yellow, Lemon Chromeyellow, Guignetsgreen and Vermillion. The vat dyestuffs of the anthraquinone series maybe incorporated in the discharge paste in the form of esters of leucocompounds, while the mineral pigment colors may be applied inconjunction with albumen or the like.

In order further to illustrate our invention, but withoutbeinglimitedthereto, the following specific example is given.

Example To a solution containing 190 parts ofpotassium dichromate in1000parts of water, sufficient gum tragacanth thickening (30:1) or cornstarchthickening is added to make a paste of required consistency.

After printing the fabric wlth a paste, the fabric has immediatelyapplied thereto by padding or by pin rolls, a solution of oxalic acid orother acid of about 19% concentration, which may or may not haveathickener I therein. The fabric is then run over dry ng' drums, and maythen be aged for 10 to 15' minutes with steam at 5 lbs. pressure. Thefabric may then be'glven if desired any sul) sequent hmshlng treatment,such as scouring, washing. etc. By the use of this process,

a fabric having a blue background with a discharge white design 18produced.

It is to be understood that the foregoing 7 example is given merely byway of illustration, and that many variations may be made thereinwithout departingfrom the spirit of our invention.

Having described our invention, what we desire to secure by LettersPatent is 1. Method of discharge printing a fabric containing organicderivatives of cellulose, which fabric has applied thereto ananthraquinone dye in the unreduced state, comprising locally applyingthereto an oxidizing agent comprising a chromate and anacid.

2. Method of discharge printing a fabric containing cellulose acetate,which fabric has applied thereto an anthraquinone dye in the unreducedstate, comprising locally applying containing cellulose acetate, whichfabric has applied thereto an anthraquinone dye in the unreduced state,comprising locally applying thereto a acid.

In testimony whereof, we have hereunto subscribed our names. 1

(AMILLE DREYFUS. GEORGE SCHNEIDER.

chromate and thenapplying an

